The braid, in general, is made in such a way to weave a plurality of layered yarns and is used to manufacture an electric wire or a hose, a binding string and is used in a water treatment filtration field.
Meanwhile, a filtration method implemented using a hollow fiber membrane applied, for example, to a water treatment field is being widely used in a filtration field, for example, an industrial waste water treatment, a sewage and waste treatment and a high water purification for a water supply. In recent years, such a filtration method is being increasingly applied to a pretreatment of a RO system, a bacteria free water for a medicine, a fish farm and a leisure facility.
The typical hollow fiber membrane, however, has a disadvantage in the way that since its tensile strength and compressive strength are low, it may be easily broken by an external impact or if it is used for a long time, a filtration reliability and a water penetration performance may be greatly degraded due to various impurities or sludge which are adhered to the surface of the membrane.
In order to resolve the aforementioned problems, a hollow fiber reinforcement membrane is developed and currently used, which is implemented in such a way that a braid weaved into a tubular shape using a filament yarn or a drawing textured yarn is employed as a reinforcing member, and a membrane thin film is coated on the surface of the braid, by which a mechanical strength (a tensile strength and a compressive strength) can be increased, thus extending a service life of the product, and a filtration reliability and a water penetration performance can be enhanced.
The above-described braid for a hollow fiber reinforcement membrane, however, has a disadvantage in the way that if a braid weaved using a filament yarn is used for the reinforcement of a hollow fiber membrane, the inner diameter of the braid can be increased; however the peeling strength of the membrane film may become weak, for which the membrane can be easily peeled off, and the service life of the hollow fiber membrane may be decreased, thus lowering the filtration reliability. If the braid weaved using the drawing textured yarn is used at a hollow fiber reinforcement membrane, the adhering force with the surface of the braid of the membrane film may be increased, which may result in an increased peeling strength, so the service life of the membrane can be increased, and the filtration reliability can be improved; however the inner diameter thereof may be decreased, for which the water penetration performance may be significantly degraded.
Moreover, when weaving a braid for a reinforcement membrane of a hollow fiber in such a way to use a filament yarn or a drawing textured yarn, since the size of the inner diameter of the braid and the circularities of the inner and outer diameters are key elements to determine the performance of the water penetration of the hollow fiber reinforcement membrane and the filtration reliability and the service life of the product, a high carbon steel wire called a piano wire of a diameter of 0.8˜2.0 mm is disposed in the center at an inner side of the woven layered yarn, wherein the diameter may differ based on the material of the layered yarn and the number of carriers of a braiding machine, in order to expand the inner diameter of the braid and enhance the circularity, and the length of the portion covered by the layered yarn may be about 5˜10 mm long, and the layered yarn is woven around the portion, thus manufacturing a braid.
When the layered yarn is woven around the steel wire, the inner diameter may be greatly expanded; however if it is woven out of the steel wire, it might be directly contracted due to the elasticity and tensile strength of the layered yarn, and it may be easily deformed during the procedures where it passes through a drawing device and the braid is loaded, for which it may become hard to maintain a circular shape.
In addition, the contraction and deformation may occur during a coating procedure of a membrane film and before or after a heat treatment, so the enhanced effects in terms of the expansion of the inner diameter of the braid and the circularities of the inner and outer diameters may be expected a little, but such effects are weak.